This Keystone Symposium will offer two concurrent meetings: "Cytokines and Cytokine Receptors: From Cloning to the Clinic" and "Molecular Mechanisms in Rheumatoid Arthritis and Related Diseases". Many important advances have been made in both of these areas of basic research over the past two years making these meetings extremely timely. These meetings are highly multidisciplinary, bringing together investigators from academia and industry representing the research disciplines of cell biology, molecular biology, immunology and biochemistry, and the clinical disciplines of hematology and rheumatology. These meetings are intended to bring together scientists who are working in competing areas and may represent different points of view. The prime objective is to present new and recent research findings that will stimulate cross-fertilization among basic and clinical investigators sharing a common interest in cytokines and mechanisms of human diseases. The meeting on "Cytokines and Cytokine Receptors" will focus on novel cytokine-controlled systems of cellular proliferation and differentiation. Areas to be emphasized include cytokine control of hematopoiesis and lymphopoiesis, mechanisms of signal transduction, and cytokine influence on both gene regulation and expression. The meeting on "Molecular Mechanisms in Rheumatoid Arthritis and Related Diseases" will emphasize the immunologic and inflammatory mechanisms that induce and perpetuate a variety of acute and chronic human diseases. Topics to be discussed include the role of environmental factors, mechanisms of genetic predisposition, T and B cell abnormalities and adhesion molecules. An important emphasis of both meetings will be on the development of new therapeutic approaches to human disease. Joint sessions will be held on recent developments in the inhibition of TNF or IL-1 action. These sessions will discuss the latest developments in the basic biology of the IL-1ra receptor antagonist, soluble IL- 1 receptors, soluble TNF receptors and antibodies to TNF. Additional presentations will provide up-to-date information on the results of clinical trials with each of these reagents. Other new forms of therapy to be discussed will include interference with T lymphocyte function through Monoclonal antibodies, peptides or vaccination, and the use of recombinant cytokines. Thus, these two concurrent Keystone symposia offer an opportunity for a unique scientific forum with interactions. between basic and clinical investigators interested in cells and cytokines in human hematologic, immunologic and inflammatory diseases.